A process for preparing siloxanyl-but-2-ene-1,4-diol compounds is described in DD-A-239 596 (Published 1st October 1986, G. Sonnek et al, VEB Chemiewerk Nunchritz), in which 2-butyne-1,4-diol is reacted with an organopolysiloxane containing Si-bonded hydrogen atoms in the presence of hexachloroplatinic acid, in which the ratio of the triple bond in the 2-butyne-1,4-diol to the SiH groups in the organopolysiloxane containing Si-bonded hydrogen atoms in the reaction is 1:1 to 1:3. The organopolysiloxane containing SiH groups is preferably employed in excess, however, the excess organopolysiloxane containing SiH groups cannot be separated from the end product after the hydrosilylation reaction. In order to avoid a reaction between the reactive hydroxyl groups in the 2-butyne-1,4-diol and the SiH groups in the organopolysiloxane, the reactive hydroxyl groups in the 2-butyne-1,4-diol must be protected by trimethylsilyl groups before the hydrosilylation reaction, and these then have to be split off again after the reaction. (See Examples of DD-A-239,596). The process thus consists of a total of three stages. In Example 11 of DD-A-239,596, the only example in which the trimethylsilyl protective groups are omitted, 2-butyne-1,4-diol is reacted directly with heptamethyltrisiloxane, which contains only one Si-bonded hydrogen atom per molecule, in a stoichiometric ratio, but the end product, 2-heptamethyltrisiloxanyl-but-2-ene-1,4-diol, is obtained only in low purity and in a moderate yield.
DD-A-255,346 (published on 30th March 1988, G. Sonnek et al, Akademie der Wissenschaften der DDR) describes a process for preparing siloxanylalkenediyl-bis-carboxylates in which siloxanyl-but-2-ene-1,4-diol compounds are reacted with saturated or unsaturated anhydrides in the presence of an esterification catalyst. In each case only 2-heptamethyltrisiloxanyl-but-2-ene-1,4-diol or 2-pentadecamethylheptasiloxanyl-but-2-ene-1,4-diol, is employed in the Examples. Thus, the examples disclose using only an organopolysiloxane having only one Si-bonded dihydroxyalkenyl group per molecule.
Organopolysiloxanes containing sulfosuccinate groups which are prepared first by reacting maleic anhydride with an organopolysiloxane containing Si-bonded hydroxyalkyl groups and then reacting the maleate group thus obtained in the organopolysiloxane with sodium bisulfite in the presence of water and a basic substance are described in EP-A-283,156 (laid-open on 21st September 1988, A. R. L. Colas et al, Dow Corning Limited). The availability of the organopolysiloxanes which contain Si-bonded hydroxyalkyl groups that are employed as starting substances is limited because according to W. Noll, Chemistry and Technology of Silicones, Academic Press, Inc., 1968, page 163, the simplest procedure for their preparation, that is the addition of organopolysiloxanes containing SiH groups to unsaturated alcohols, cannot be employed because the SiH bond is also reactive towards the C-OH group.
Therefore, it is an object of the present invention to provide organopolysiloxanes which contain sulfosuccinate groups that have better surface-active properties than was known heretofore. A further object of the present invention is to provide organopolysiloxanes which can be prepared in good yields and by a simple process.